Effects on river macroinvertebrate communities of tsunami propagation after the 2011 Great East Japan Earthquake

Abstract

Summary The 2011 Great East Japan Earthquake generated extreme tsunami waves that entered river mouths, causing strong and long‐distance propagation along the water corridors. This study reports the first empirical survey of this rare and extreme ecological impact of tsunami propagation on river communities. We sampled macroinvertebrate communities at 15 river sites on the Sendai Plain in Northeast Japan along a gradient of tsunami disturbance intensity [i.e. altitude: range = 1–29 m above sea level (a.s.l.)] two and 16 months after the earthquake. In comparison with data collected before the tsunami, we found evidence of significant reductions in taxon richness (−54% on average) and total abundance (−91%) after the tsunami in inundated river reaches (up to 25 km from the river mouth). There were large spatial variations in local impacts, with altitudes of 7–9 m a.s.l. separating heavily damaged inundated communities from intact non‐inundated communities. The degraded communities exhibited variable recovery rates extending beyond 16 months after the tsunami. Mobility trait analysis revealed a relatively rapid recovery of swimmers (e.g. Baetis), reflecting their high mobility and active drift behaviours in the recolonisation phase. We observed the rare phenomenon of ‘upstream drift’ of marine worms (Phyllodocidae) to freshwater rivers in three of the 10 inundated sites. These survived in fresh water for up to 14 months, suggesting that some marine‐derived immigrants can persist in fresh water for extended periods.

Ecological effects of extreme climatic events on riverine ecosystems: insights from Australia

“…Recovery of freshwater fauna following saltwater flooding is likely influenced by dispersal characteristics, with active dispersal (e.g. swimming) contributing to rapid recovery (Watanabe et al, 2014).…”

A massive tsunami promoted gene flow and increased genetic diversity in a near threatened plant species

“…The Great Tohoku Earthquake (magnitude 9.0 [M w ]) in Japan, the fourth largest earthquake in the world since 1900, also caused a giant tsunami 23 that resulted in substantial alteration of biological community compositions 24 – 26 . In the northeast Honshu coastal region (N36° to N40°; Fig.…”

Immediate impact of the tsunami associated with the 2011 Great East Japan Earthquake on the Plecoglossus altivelis altivelis population from the Sanriku coast of northern Japan

“…The tsunami also likely impacted those species through direct disturbance and habitat destruction. The extent of damage to other fish and benthic animals caused by the tsunami and their restoration vary depending on the species (Masuda 2013;Nakayama et al 2013;Seike et al 2013;Watanabe et al 2014). Therefore, comprehensive studies about how the 2011 tsunami impacted coastal ecosystems will contribute to a full understanding of the vulnerability of local ecosystems to disturbances and the ecological processes forming local community structure.…”

“…The tsunami similarly affected riverine macroinvertebrate communities far upstream from the river mouth during inundation (Watanabe et al 2014). Some studies have reported that some species recolonized and other rare species invaded this area within several months after the tsunami (Masuda 2013;Seike et al 2013;Watanabe et al 2014).…”